1. Field of the Invention
The present invention relates to a paper tray for an electrophotographic apparatus and, more specifically, to a paper detection device for a paper tray that is inserted into an electrophotographic apparatus in a direction perpendicular to the paper pickup direction.
2. Background Art
An electrophotographic apparatus can be either one of a laser printer, an electronic copier, a facsimile machine, or any versatile office machine. The general operation of an electrophotographic apparatus starts with paper being loaded from a supply tray and then transported through to a high pressure transfer roller. The high pressure transfer roller transfers the toner image from the photoconductive drum onto the sheet of paper. Subsequently, the paper is transported to a fixing device that fuses the toner image onto the paper using both heat and pressure rollers.
A paper tray may be mounted on the bottom of an electrophotographic apparatus body to sequentially feed individual cut sheets of paper to the electrophotographic apparatus. Some paper trays are designed so that the direction that the paper tray is inserted and withdrawn in is perpendicular to the paper pickup direction. When cut sheets of paper are in the paper tray, a pickup roller is in contact with the topmost sheet in the stack. The pickup roller then feeds the cut sheets, one by one, into the electrophotographic apparatus. A paper detection device for use with a paper tray that contains a paper stand that moves perpendicularly relative to the base of the paper tray. Paper is stacked on the paper stand and the topmost sheet is removed by a pickup roller that exerts a frictional force on the paper.
After a user inserts paper into the paper tray, the tray is inserted into the electrophotographic apparatus. The side of the paper stand that is along the edge at which the paper is picked up by the pickup roller is displaced in an direction away from the base of the paper tray. This brings the topmost sheet of paper into contact with the pickup roller to allow the paper to be fed into the apparatus.
An optical sensor is installed on the apparatus body and an optical transmission hole is positioned at one side of the paper stand aligned in opposition with the optical sensor. Thus, when paper is in the paper tray, light generated by the optical sensor is reflected off of the paper and received by the optical sensor. When the paper tray is empty the light emitted by the optical sensor passes through the transmission hole and the optical sensor detects the absence of paper.
Different techniques for monitoring the paper in a paper tray are shown, for example, in U.S. Pat. No. 4,879,575 to Maruta entitled Copying Apparatus With Provision for Delayed Reset in the Event of Paper Exhaustion, U.S. Pat. No. 5,028,041 to Kobayashi entitled Image Forming Apparatus With Sheet Feeder, U.S. Pat. No. 5,332,207 to Oonishi entitled Paper Feeder and an Image Forming Apparatus Provided With the Same, U.S. Pat. No. 5,446,524 to Koike entitled Image Forming Device with a Function of Selecting Recording Paper, U.S. Pat. No. 4,963,941 to Negishi entitled Form Feeding Control Device, and U.S. Pat. No. 5,204,726 to Choi entitled Copying Paper Feed Sensing Device for a Copying Apparatus. The contemporary art for detecting paper in paper trays does not provide a device that is economical to manufacture, that uses only simple components, that will function with transparencies and other transparent cut mediums, that will detect an empty paper tray, that are designed for paper trays that attach to electrophotographic apparatus that engage the paper tray in a direction substantially perpendicular to the paper pickup direction.
As such, I believe that it may be possible to improve on the contemporary art by providing a device that detects the presence of paper in a paper tray, that is designed for a paper tray that is inserted into an electrophotographic apparatus in a direction substantially perpendicular to the paper pickup direction, that is economical to manufacture, that is constructed using simple components, and that accurately functions when using transparent cut medium.